In the deep-sea oil and gas production, the oil and gas fields on the bottom of the sea are supplied with electric energy, pressure pipelines and command information via branched subsea supply lines, so-called umbilicals, originating from a central production platform. The expansion of oil and gas fields is so large that individual subsea supply lines can reach lengths of up to 150 km.
A subsea supply line failing can lead not only to significant economical shortages caused by production downtime but also to great risks to the environment, the production plant and the personnel on the plant caused by production installations which have become uncontrollable.
Identifying and quickly localizing damage to the subsea supply line, in particular insulation faults on an electric conductor run in the subsea supply line, are therefore a very high priority especially in the scope of supply lines.
The technology available for solving these safety related tasks, however, is limited by the specific requirements posed by the deep sea surroundings. This explains why insulation faults on electric conductors run in the subsea supply line are mostly localized manually by sending out divers, small submarines and ships. The expenditure and thus the costs of locating faults are accordingly high.
Methods of time domain reflectometry (TDR) for localizing faults on an electric conductor by means of reflected measuring signals are known from the state of the art. Using TDR technology, however, seems to be limited to pipe sections having a maximum length of 50 km with currently available technology.
Building upon the realization that electrolytic processes take place at a faulty insulation point between the exposed metallic conductor material, such as copper, and the saline seawater under the influence of an applied DC voltage when an electric line is run in the seawater, a regeneration method was proposed in the patent disclosure WO 2014/128439 A1, which uses the electrochemical reaction for repairing insulation fault locations. By periodically varying the amplitude of the DC voltage and by optionally changing the polarity, the process of forming gas at the faulty location during electrolysis can be influenced such that the insulation properties can be repaired. A targeted tracking of the insulation fault location was not disclosed.